rageingtelephone

[quote name='Mr. Foxen' timestamp='1378997625' post='2207552'] Justin is Subthumper on here. I send ampeg stuff to him, because I don't like working on it, despite the rep, the stuff is plain badly made. Throwing valves at a problem amp is rarely the way, problem is elsewhere, if its more than about 15 years old, its probably capacitors, ampeg way underspecced them and they die pretty early. finding the problem is fun because of the way ampeg make the amps, can't run them open to figure whats going on without specialist looms, forcing you to go to Ampeg approved techs who just bulk replace entire PCBs and charge you accordingly. [/quote] Yeah I have gathered they are pigs to work on! In fact I think Justin did swap out some caps last time I gave the head to him. Im not sure exactly but I think it may be from the early 1990s, if it's any help my amp is the exact same model as the svt2pro you can see half way down the page [url="http://www.chambonino.com/work/ampeg/amp4.html"]here[/url] (the one with blue and red writing for the "svt II pro" part). So think I should carry on with these seemingly endless attempts at repair?

[quote name='6v6' timestamp='1378995943' post='2207520'] Doesn't sound right, the tubes must be biased too hot IMO, or there's some other fault with the amp. Good quality tubes should last a fair while provided they're biased properly, and you're not mismatching the load (is your cab the right impedance?), like at least a couple of years even with fairly regular gigging. [/quote] Yeah that's what I thought. I have always made sure to adjust the bias properly using the controls on the back of the head when replacing the power valves. And yes I am using a 4ohm cab with the switch also set to 4ohms on the back of the head. Hmm

[quote name='chris_b' timestamp='1378985389' post='2207317'] Where are you? Where do you get the amp serviced? [/quote] I reside in Bristol. So far I have had it serviced by an independant guy called Jesse James and later on by Justin @ [url="http://www.heronmusic.co.uk/"]Heron Music[/url].

So I have been using my Ampeg Svt2pro for over three years now and no matter how many times I get it serviced/replace the valves, it ends up being a moody little piece of work. I just replaced the power valves with a 6550/JJ-Tesla- AMPEG SEXTET 5 months ago. All was peachy for a while then 3months in it started making the tell tale detuned radio sounds on occasion, then the next day it would sound great again. One day working perfectly, the next day making weird 'helicopter' sounds etc. It seems when it sounds great I would forget/mentally ignore about how crap it could also sound sometimes. Now when I tap the amp head itself you can hear it through the cab, which I presume means the valves have already gone microphonic? Surely this is burning the valves out too quickly, for the sound and my pocket! I am tired of this and am debating getting it serviced one last time then replacing it with an alternative. Any thoughts? I love the sound of it when the bloody thing is on top form, any suggestions as to a different head I should get? I have been looking at Aguilar and Eden heads. Btw I am using an ampeg 6x10 Classic cabinet. And please tell me if you think this ampeg might be saved some miraculous way. Cheers!

[quote name='DHA' post='1019931' date='Nov 11 2010, 12:27 PM']Did you set the bias with a 4 or 8ohm cab attached?[/quote] With the 4ohm cab

[quote name='DHA' post='1012377' date='Nov 4 2010, 06:08 PM']Might not be the problem but very bad advice from your tech guy. With valve amps it is important to have the correct speaker impedance connected as this sets the reflected load on the power tubes via the output transformer. I think the power tubes might well be blown. When you changed the valves it should have been re-biased as well. sorry, Dave[/quote] Thanks Dave, yeah I did change all six of the power valves not too long ago and used the bias controls on the back. I've also taken them all out to check and all seem fine (no cloudyness etc), and also all glow as normal when amp is turmed on. So i dont think the tubes are blown... could a dirty switch cause any of the trouble I mentioned before? I was aware of the dangers of not matching the impedance correctly, but as far as I knew I thought it was only if the impedance of the speaker was lower than the amp that damage could occur? Cheers, Thom. I should also mention, whilst playing another show the other day it started out fine and normal, then the same volume drop happened after a couple tunes. I was using the correct impedance cab this time.....!

I think my ampeg is early 90's? It says 'svt 2 pro' in all blue writing except the 'v' which is red. The serial number simply says 'D'. I normally play this amp through an Ampeg 6x10 4Ohm cab live, but at smaller shows and rehearsals I use an SWR goliath junior III rated at 8ohms unfortunately. I got advice from a tech guy and he say it should be fine to run through an 8Ohm cab instead of 4Ohms, and it does work albeit a strange distortion when bass guitar is turned to half volume. BUT a couple of nights ago half way through a number a huge volume drop occurred. I thought the amp had shutoff, so I turned it off and on again to no avail, only being able to get enough volume with the gain and master much higher than normal. I should mention, a few days before this happened, a loud static noise introduced itself, going up and down in volume randomly. Even with the input gain at zero and the mute switch on... the only thing that affects it is the master volume or putting the amp into standby. I have replaced all the power valves about four months ago. I read that it could be a loose/dirty pin in one of the valves so i took them all out, inspected them and wiggled them. The master volume pot is also dirty as loud pops happen if you dont twist the knob alot to clean before switching the amp on. Upon reassembling the amp, there seemed to be no change. Anyone got and ideas?! Help will be much appreciated!! Thanks.

Sold me a bass in hardcase, perfect! Package was at my door in bristol from Ireland within 2 days. No need to worry when dealing with Gareth, recommended!